The present invention relates to a continuous compression-type dewatering apparatus for concentrated sludge, and more particularly to a compression-type dewatering apparatus for sludge that is difficult to filter, such as sewage sludge.
A filter press, a belt press, and a screw press (refer to Japanese Patent Application Publication No. 44-2929 and Japanese Unexamined Patent Application Publication No. 6-695, for example) are known types of pressurized dewatering apparatuses for dewatering difficult-to-filter sludge, such as sewage sludge.
With a filter press, however, there is a tendency for clogging to occur in the filter cloth used as a filter material, and it is difficult to renew the filter cloth by cleaning.
With a belt press, in order to sustain the functions of the filter cloth used as a filter material, it is necessary to continuously clean the filter cloth as dewatering is performed. For this reason, a large amount of cleaning water is consumed. Additionally, because sludge is only pressurized at the outer peripheral surfaces of a large number of pressure rolls arrange in a line, a large amount of installation space is required, and the filtering efficiency is low.
With a screw press, because the filtering surface is divided on the inner surface of a cylindrical metal filter material, a large amount of installation space is required, and the filtering efficiency is low.
In consideration of the above-described problems occuring in the past, it is an object of the present invention to provide a continuous compression-type denaturing apparatus having simple construction, small size, and a small installation space, and which has a high filtering efficiency, and operates at a low speed, so as to require only a small drive source.
To achieve the above-noted object, a first aspect of the present invention has a filter chamber (3), a drive shaft (17), vanes (15), and a supply path (50). The filter chamber (3) is divided into an annular plate (2) and two side plates (1, 1). The drive shaft (17) passes through the center axis of the annular plate (2) and through the inside of the filter chamber (3), and is freely rotatable with respect to the filter chamber (3). The vanes (15) are disposed within the filter chamber (3), are fixed with respect to the drive shaft (17), extend from the drive shaft (17) toward the annular plate (2), and rotate in concert with the drive shaft (17). The supply path (50) passes through the inside of the drive shaft (17) and supplies raw fluid to the filter chamber (3). The vanes (15) have two side edges (15a, 15a) that face the side plates (1, 1) and an end edge (15b) that faces the annular plate (2).
At least one of the side plates (1, 1) includes a filter element (4) for separating the raw fluid into a liquid and a cake. The annular plate (2) includes an ejection port (7) for the cake.
By the action of the inflow pressure of the raw fluid from the supply path (18) to within the filter chamber (3) and the rotation of the vane (15), the filtered fluid flows out f rom the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) from the ejection port (7).
In the above-noted configuration, the raw fluid flows into the center part of the filter chamber (3) from the supply path (50). After having flowed into the filter chamber (3) the raw fluid receives the flow pressure thereof and moves toward the side plate (1), and is filtered by the filter element (4). The filtered fluid passes through the filter element (4) and is ejected from the filter chamber (3), the cake remaining on the filter element (4). The remaining thin film of cake is scraped by side edge (15b) of the rotating vanes (15), and is sent toward the outer periphery by the vanes (15). When the cake moves, a rotational friction force develops between the cake and the vanes (15), so that sliding resistance is generated between the cake and the side plate (1). For this reason, the cake is further filtered as it moves, so that the water content is lowest in the region of the annular plate (2). The cake with low water content is ejected via the ejection port (7).
The filter element (4) can be provided on each of the side plates (1), and can be provided over substantially the entire area of the side plate (1). By doing this, the filtering surface area with respect to the raw fluid is increased, thereby further increasing the filtering efficiency.
The annular plate (2) can include a second filter element (9) for separating the raw fluid into a liquid and a cake. By doing this, the filtering surface area with respect to the raw fluid is increased, thereby further increasing the filtering efficiency. The cake on the filter element (9) is pressured by the end edge (15b) of the vane (15) and further dewatered, so that a cake with a further decreased water content is ejected from the ejection port (7).
The filter element (4) can be a substantially donut-shaped screen (4) with a large number of fine holes. The second filter element (9) can be a screen (9) with a large number of fine holes.
The side plate (1) can have a screen (4), an annular outer frame (5) fixed to the outer peripheral edge of the screen (4), an annular inner frame (6) fixed to the inner peripheral edge of the screen (4), and a rib (5a) that links the outer frame (5) and the inner frame (6). By doing this, mounting of the screen (4) to the side plate (1) is facilitated, and the strength of the screen (4) is increased.
The supply path (50) can have a main supply path (18) within the drive shaft (17), a supply port (19) formed in the drive shaft (17) that opens toward the main supply path (18), and a linking path (11) adjacent to the drive shaft (17) on the side of the vane (15) and linking the supply port (19) and the filter chamber (3).
In the above-noted configuration, the raw fluid flows from the main supply path (18) through the supply port (19) and the linking path (11) into the filter chamber (3) from the side of the vane (15). The position of the supply port (19) is not particularly restricted, as long as it is on the side of the vane (15). In contrast, in the case in which the raw fluid is directly supplied from the main supply path (18) into the filter chamber (3), it is necessary that a port for supplying be formed in the part of the drive shaft (17) facing the filter chamber (3). Therefore, in order that the vane (15) be securely fixed by the drive shaft (17), there is the possibility of an increase in the material thickness of the drive shaft (17). When the material thickness of the drive shaft (17) increases, this can bring with it an increase in the weight and size of the apparatus.
With regard to this point, according to the above-noted configuration it is possible to form the supply port (19) at a location that does not present a problem with regard to strength, thereby limiting the increase in weight and size of the apparatus.
The vanes (15, 63, 65, 67) can have operative surfaces that are forward in the rotational direction of the drive shaft (17), and the linear shape of the operative surface on a cross-section perpendicular to the drive shaft (17) can be substantially the same, and not dependent upon the location on the cross-section in the axial direction of the drive shaft (17).
The operative surface (52) on the cross-section perpendicular to the drive shaft (17) can be represented by a line along a reference straight line (68) passing through the center of the drive shaft (17).
The operative surface (52) on the cross-section perpendicular to the drive shaft (17) can be represented as a line along reference curved lines (54, 64) extending from the drive shaft (17), and a tangent line (56) at an arbitrary point on the reference curved lines (54, 64) can be inclined towards the rear of the rotational direction of the drive shaft (17) with respect to a straight line (57) passing through the arbitrary point and the center of the drive shaft (17).
The vanes (15, 63) in the above-noted configuration have a function of sending the cake in a radial direction, and a function of generating a filtering force with respect to the cake. The filtering force with respect to the cake is obtained as a force of repulsion with respect to a sliding resistance between the vanes (15, 63) and the side plate (1).
The reference curved line (64) can be can be a logarithmic spiral having an intersecting angle (xcex1) with the tangent line (56) and the straight line (57) that is constant and not dependent upon the position of the arbitrary point.
Because the intersection angle (xcex1) is constant, the vane (63) in the above-noted configuration, in proximity to the annular plate (12), where the water content of the cake is reduced, there is an increase in the rotating wedge operating force and the force which moves the cake in a radial direction along a curved line, so that a large shear force is applied to the cake.
The operative surface (52) in the cross-section can be represented by a piecewise linear curve (62) formed by a plurality of straight line segments.
In the above-noted configuration, the vane (67) is easy to manufacture and provides sufficient strength.
The vanes (15, 63, 65, 67) can have a rear surface (53) to the rear in the rotation direction of the drive shaft (17) and a rib (27) which protrudes from the rear surface (53) and reinforces the vane (15).
According to the above-noted configuration, the strength of the vanes (15, 63, 65, 67) is increased. For this reason, a rotating wedge action is achieved with respect to the cake, which has a reduced water content and increased sliding resistance.
A scraper (26) in proximity to the side plate (1) can be provided on at least one side edge (15a) of the vane (15).
According to the above-noted configuration, the thin film cake on the filter element (4) with high filter resistance is scraped off, thereby successively renewing the filter elements (4). It is therefore possible to perform continuous filtering operation over a long period of time.
A resin coating can be applied to the operative surface (52).
According to the above-noted configuration, the sliding resistance of the cake with respect to the operative surface (52) when the cake is compressed during rotation is reduced. Therefore, in addition to an increase in the operating efficiency of the apparatus, it becomes difficult for the cake to rotate in concert with the vane (15).
The above-noted apparatus according to the first aspect can be provided with valve mechanisms (8, 8a) that increase and decrease the amount of opening of the ejection port (7).
According to the above-noted configuration, the amount of opening of the ejection port (7) is adjusted by the valve mechanisms (8, 8a), so that the cake is subject to back pressure, dewatered under compression, and ejected from the ejection port (7).
The valve mechanism (8) can have a pair of rotating shafts (28, 28) rotatably supported with respect to the opposing edge of the ejection port (7), a pair of dampers (29, 29) fixed to each of the rotating shafts (28) which open and close the ejection port (7), a cylinder (32) having a rod (33), and two links (30, 30) that link the rod (33) and the rotating shafts (28, 28), convert the reciprocating motion of the rod (33) to rotational motion of the rotating shafts (28, 28) and transmit this motion.
In the above-noted configuration, the amount of opening of the ejection port is adjusted by a valve (8) having a simple construction. As a result, back pressure is received, and compression dewatering is done, so that a cake having substantially uniform water content is ejected from the center of the ejection port (7).
The valve mechanism (8a) can have a rotating shaft (28a) rotatably supported with respect to the ejection port (7), a damper (29a) fixed to the rotating, shaft (28a) that opens and closes he ejection port (7), a cylinder (32) having a rod (33), and a lever (43) that links the rod (33) and the rotating shaft (28a), converts reciprocating motion of the rod (33) to rotational motion of the rotating shaft (28a), and transmits this motion.
In the above-noted configuration, the amount opening of the ejection port (7) is adjusted by the valve mechanism (8a) vz having a simple construction. As a result, back pressure is received, and compression dewatering is done, so that a cake having substantially uniform water content is ejected from the ejection port (7).
An apparatus according to the above-noted first aspect, a cleaning nozzle (34) can further be provided for the filter element (4). The cleaning nozzle (34) can be disposed in opposition to the filter element (4) on the outside of the side plate (1).
According to the above-noted configuration, when operation of the apparatus is ended, cake remaining on the filter element (4) is removed well by cleaning water discharged from the cleaning nozzle (34).
A plurality of the vane (15) in the above-noted first aspect can be provided. By doing this, even for a raw fluid that is difficult to filter, there is an increase in the shear force and the transporting force acting one the cake, so that the cakes are pressurized and transported with good balance, thereby achieving cakes having a low water content.
The side plates (1, 1) can be disposed so as to be substantially mutual parallel, with the distance (D) from an end edge (15b) of one vane (15) to an adjacent vane (15) to the rear thereof with respect to the direction of rotation established as being greater than the length (L) between the side plates (1, 1). By doing this, the filter surface area that tries to stop the cake can be made more than twice the operative surface (52) of the vane (15) that attempts to move the cake, effectively preventing the in-concert rotation of the cake.
A continuous compression-type dewatering apparatus according to a second aspect of the present invention has a plurality of filter units (70) provided inparallel, and a drive shaft (17). Each filter unit (70) has a filter chamber (3) divided into to an annular plate (2) and two side plates (1, 1), and a vane (15) disposed within the filter chamber (3). The annular plates (2, 2) are disposed about a common axis. The drive shaft (17), passes through the center axis of the annular plates (2, 2), and through the inside of the filter chambers (3, 3), and is freely rotatably with respect to the filter chamber (3).
The vane (15) is fixed with respect to drive shaft (17), extends from the drive shaft (17) toward the annular plate (2), and rotates in concert with the drive shaft (17). A supply path (50) that supplies raw fluid to the filter chamber (3) is formed inside the drive shaft (17). The vane (15) has two side edges (15a) that face the side plates (1, 1), and an end edge (15b) that faces the annular plate (2). Of the side plates (1, 1) of the filter unit (70), at least one side plate includes a filter element (4) for the purpose of separating the raw fluid into a liquid and a cake. The annular plate (2) includes an ejection port for the cake. By the action of flow pressure of the raw fluid from the supply path (50) to within the filter chamber (3) and the rotation of the vane (15), the filtered fluid flows out form the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) from the ejection port (7).
In the above-noted configuration, because a plurality of filter chambers (3) are provided in parallel, it is possible to perform simultaneous filtering of a large quantity of raw fluid. Additionally, the amount of space occupied by the apparatus is reduced.